Heart Rate Variability Guided Physical Activity and Exercise Prescription in Individuals With Knee Osteoarthritis

Assessed using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain subscale. Higher scores mean more discomfort. The WOMAC pain subscale include five items for pain (scores range from 0 to 20).

Assessed using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) function subscale. Higher scores mean more difficulty with daily tasks. The WOMAC function subscale include 17 items for functional restriction (scores range from 0 to 68).

Client service recipient inventory (CSRI) will utilised to assess healthcare resource utilisation.

Quality-adjusted life-years (QALYs) will serve as outcome metric for economic evaluation, derived from the 5-level EuroQol instrument (EQ-5D-5L). Unadjusted mean costs and cost differences between HRV-G and TRD-G exercise groups will be examined for aggregate and disaggregated cost components, including intervention costs, healthcare service use, and pharmaceutical expenditures. Total cost differences (ΔC) and effect differences (ΔE) will be estimated, adjusting for baseline demographic and health characteristics. Responses from the EQ-5D-5L will be converted into utility scores, which will then be used to calculate QALY changes over the study period. The incremental cost-effectiveness ratio (ICER) will be computed using the formula ICER = ΔC/ΔE.

Assessed using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain subscale. Higher scores mean more discomfort. The WOMAC pain subscale include five items for pain (scores range from 0 to 20).

Assessed using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) function subscale. Higher scores mean more difficulty with daily tasks. The WOMAC function subscale include 17 items for functional restriction (scores range from 0 to 68).

The Arthritis self-efficacy scale (ASES) consists of 20 items that assess a patient's confidence in controlling pain, physical function, and other disease-related factors. The scale has three parts: pain management, function, and other symptoms like fatigue. Each question asks the respondent to rate their self-efficacy on a scale from 10 to 100, with 10 meaning "very uncertain" and 100 meaning "very certain" about their capacity to do particular tasks or deal with symptoms. Therapists give the questionnaire to patients and tell them to think about how confident they usually feel during the past week when they answer. To get subscale scores, the scores in each domain are added together. Higher scores indicate greater perceived self-efficacy.

The Pittsburgh Sleep Quality Index (PSQI) used to measure the quality and patterns of sleep in adults. It identify sleep quality between "poor" and "good" sleep by utilizing seven domains: subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbances, use of sleep medication, and daytime dysfunction. A lower PSQI score indicates better sleep quality, with scores of ≤5 considered good and ≥5 indicating poor sleep quality.

The Center for Epidemiologic Studies Depression Scale (CESD) is a widely used self-report scale designed to measure depressive symptoms in the general population, consisting of 20 items that assess how often individuals have experienced specific symptoms over the past week. The score is the sum of the 20 questions. Possible range is 0-60. A score of 16 points or more is considered depressed.

The Patient Specific Functional Scale (PSFS) is a self-reported valid, reliable, and responsive outcome measure for patients with back, neck, knee and upper extremity problems. It has also been shown to have a high test-retest reliability in both generic lower back pain and knee dysfunction issues. It is also clinically responsive to changes over time with chronic pain patients. Patients are asked to identify up to five important activities they are unable to perform or are having difficulty with as a result of their problem eg putting socks on, shopping. Patients are asked to rate their current level of difficulty associated with each activity on an 11-point scale from 0 (unable to perform) to 10 (able to perform at prior level). Higher the score better the function.

The 30 second chair stand test (30sCST) requires participants to rise fully from a seated position in an unarmed, straight-backed chair (seat height: 45 cm) and return to a seated position until fully seated. The total number of chair-stand repetitions performed within a 30-s interval will be recorded. Participants will engage in two slow-paced practice repetitions prior to formal testing to ensure comprehension.

The 40-m fast-paced walk test (40MFPW) requires participants to walk as quickly and safely as possible along a 10-m walkway, turning around a cone positioned 2 m beyond each end of the walkway, resulting in a total distance of 40 m. Participants may utilize a walking aid if necessary, and the duration for task completion will be documented [22].

The stair-climbing test (SCT) will require participants to ascend and descend nine stairs, each with a step height of 20 cm, as quickly as possible while ensuring safety. A handrail will be provided for participants who wish to utilize it or require walking aids. The duration for participants to complete the ascending and descending tasks will be recorded.

Motion capture system will be utilized for gait assessment.

An isokinetic dynamometry will be used for the assessment of Quadriceps and Hamstring muscle strength

Bertec balance system will be used for the assessment of Single and double leg standing balance.

All participants will conduct HRV measurements, starting one week before the intervention and continuing until its completion. HRV will be measured each morning immediately after awakening and bladder voiding, with participants remaining in the supine position for 5 minutes. The validated smartphone application, "HRV4Training" (http://www.hrv4training.com/) will be used to record HRV data [31]. The analysis provides the root mean square of successive differences between R-R intervals (root mean square successive differences [rMSSD]), derived via photoplethysmography. The rMSSD is preferred for its reliability over other HRV indices. To normalise data distribution, HRV values will be log-transformed using the natural logarithm (Ln) before statistical analysis. A 7-day rolling average (Ln rMSSD7d) will be computed, and HRV parameters will be calculated during both the familiarization period and on a weekly basis throughout the experimental phase.

The feasibility and usability of the HRV device for optimising home exercise programme will be evaluated using the System Usability Scale (SUS). The HRV device will be considered a viable tool for rehabilitation and home exercise optimization in individuals with KOA if it achieves an average SUS score of 70 points or higher.